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<ul><li>利用继承可以将一些通用的样式，统一设置到共同的祖先上。这样只需要设置一次即可让所有的元素都具有该样式</li> <li>并不是所有的样式都会被继承。比如背景相关，布局相关等样式都不会被继承。</li></ul></li></ul> <h2 id="_2-选择器的权重"><a href="#_2-选择器的权重" class="header-anchor">#</a> 2.选择器的权重</h2> <p>当通过不同的选择器，选中相同的元素，并且为相同的样式设置不同的值时，此时就发生了样式的冲突，样式冲突时，样式由选择器的权重（优先级）决定选择器的权重。</p> <table><thead><tr><th>选择器</th> <th>权重</th></tr></thead> <tbody><tr><td>行内样式</td> <td>1，0，0，0</td></tr> <tr><td>ID选择器</td> <td>0，1，0，0</td></tr> <tr><td>类和伪类选择器</td> <td>0，0，1，0</td></tr> <tr><td>元素选择器</td> <td>0，0，0，1</td></tr> <tr><td>通配选择器 *</td> <td>0，0，0，0</td></tr> <tr><td>继承的样式</td> <td>没有优先级</td></tr></tbody></table> <p>比较优先级时，需要将所有的选择器的优先级进行相加计算，最后优先级越高，则越优先显示（分组选择器时单独计算的）</p> <ul><li>选择器的累加不会超过其最大的数量级，类选择器再高也不会超过ID选择器</li> <li>如果优先级计算后相同，则优先使用靠下的样式</li> <li>可以再某一个样式后添加<code>!important</code>，此时该样式会获取到最高的优先级，甚至超过内联样式，注意：再开发中一定要慎用。</li></ul> <div class="language-HTML line-numbers-mode"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>style</span><span class="token punctuation">&gt;</span></span><span class="token style"><span class="token language-css">
    <span class="token selector">#box1</span> <span class="token punctuation">{</span>
        <span class="token property">background-color</span><span class="token punctuation">:</span> orange<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token selector">div#box1</span> <span class="token punctuation">{</span>
        <span class="token property">background-color</span><span class="token punctuation">:</span> yellowgreen<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token selector">.red</span> <span class="token punctuation">{</span>
        <span class="token property">background_color</span><span class="token punctuation">:</span> red<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token selector">div, p, span</span> <span class="token punctuation">{</span>
        <span class="token property">backgorund-color</span><span class="token punctuation">:</span> aqua<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>style</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>box1<span class="token punctuation">&quot;</span></span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>red<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
    选择器的权重
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br></div></div><p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211101956362.png" alt="样式比较"></p> <h2 id="_3-长度单位"><a href="#_3-长度单位" class="header-anchor">#</a> 3. 长度单位</h2> <p><strong>像素：</strong> 显示器屏幕实际是由一个个的小点（单位色块，即像素）构成的</p> <ol><li><strong>像素和分辨率的关系</strong></li></ol> <p>​		<strong>分辨率 = 水平方向像素 * 垂直方向像素</strong></p> <ul><li>不同屏幕的像素大小不同，像素越小，屏幕显示效果越清晰。所以同样的像素大小在不同的设备上显示的效果是不同的。</li> <li>同一台设备的像素大小是不变的，把图片放大超过100%时占的像素点多，但是图像也会变模糊。</li></ul> <p>​	2. <strong>屏幕实现图片放大和缩小的原理</strong></p> <ul><li>其实是设备通过算法对图像进行了像素补足。同理，把图片按小于100%缩放时，也是通过算法将图片元素减少。</li></ul> <p><strong>百分比</strong>：也可以将属性设置为相对于其父元素属性的百分比</p> <ul><li>使子元素跟随父元素的改变而改变</li></ul> <p><strong>em：</strong> em是相对于元素的字体大小来计算的，<code>1em = &lt;self&gt;.font-size * 10</code></p> <ul><li>也就是说，em值会根据元素本身的字体大小改变而改变，浏览器默认的font-size为16px</li></ul> <p><strong>rem：</strong> rem是相对于根元素的字体大小来计算的, <code>1em = &lt;root&gt;.font-size * 10</code></p> <ul><li><p>也就是说 rem的值会根据根元素的字体大小改变而改变</p> <div class="language-HTML line-numbers-mode"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>style</span><span class="token punctuation">&gt;</span></span><span class="token style"><span class="token language-css">
    <span class="token selector">*</span> <span class="token punctuation">{</span>
        <span class="token property">font-size</span><span class="token punctuation">:</span> 24px<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    
    <span class="token selector">.box1</span> <span class="token punctuation">{</span>
        <span class="token property">width</span><span class="token punctuation">:</span> 200px<span class="token punctuation">;</span>
        <span class="token property">height</span><span class="token punctuation">:</span> 200px<span class="token punctuation">;</span>
        <span class="token property">background-color</span><span class="token punctuation">:</span> orange<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    
    <span class="token selector">.box2</span> <span class="token punctuation">{</span>
        <span class="token property">width</span><span class="token punctuation">:</span> 50%<span class="token punctuation">;</span>
        <span class="token property">height</span><span class="token punctuation">:</span>50%<span class="token punctuation">;</span>
        <span class="token property">background-color</span><span class="token punctuation">:</span> aqua<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    
    <span class="token selector">.box3</span> <span class="token punctuation">{</span>
        <span class="token property">font-size</span><span class="token punctuation">:</span> 20px<span class="token punctuation">;</span>
        <span class="token property">width</span><span class="token punctuation">:</span>10em<span class="token punctuation">;</span>
        <span class="token property">height</span><span class="token punctuation">:</span>10em<span class="token punctuation">;</span>
        <span class="token property">background-color</span><span class="token punctuation">:</span> greenyellow<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token selector">.box4</span> <span class="token punctuation">{</span>
        <span class="token property">font-size</span><span class="token punctuation">:</span> 20px<span class="token punctuation">;</span>
        <span class="token comment">/*
        当用rem时，不管怎么改变本元素的font-size都不会变。
        需要定义root元素的font-size才可以
        */</span>
        <span class="token property">width</span><span class="token punctuation">:</span> 10rem<span class="token punctuation">;</span>
        <span class="token property">height</span><span class="token punctuation">:</span> 10rem<span class="token punctuation">;</span>
        <span class="token property">background-color</span><span class="token punctuation">:</span> red<span class="token punctuation">;</span>           
    <span class="token punctuation">}</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>style</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>box1<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>box2<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>     
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>box3<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>box4<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br><span class="line-number">40</span><br><span class="line-number">41</span><br><span class="line-number">42</span><br><span class="line-number">43</span><br><span class="line-number">44</span><br></div></div><p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211101957449.png" alt="尺寸"></p></li></ul> <h2 id="_4-颜色单位"><a href="#_4-颜色单位" class="header-anchor">#</a> 4. 颜色单位</h2> <p>css<strong>中的颜色名称</strong></p> <ul><li>在css中可以直接使用颜色名来设置颜色，比如：red， orange， yellow， blue等</li> <li>其中有140多个颜色名称时所有浏览器都支持的，但是有个问题，在css中直接使用颜色名称非常不方便。</li></ul> <h3 id="rgb值"><a href="#rgb值" class="header-anchor">#</a> RGB值</h3> <p>RGB通过三原色的不同浓度来调配出不同的颜色</p> <ul><li>语法：<code>RGB(red, green, blue)</code></li> <li>范围：每一种颜色的范围在0~255（0%~100%）之间</li></ul> <h3 id="rgba"><a href="#rgba" class="header-anchor">#</a> RGBA</h3> <p>在RGB的基础上增加了一个a表示不透明度</p> <ul><li>语法：<code>RGBA(red, green, blue, .5)</code></li> <li><code>1</code>表示完全不透明</li> <li><code>0</code>表示完全透明</li> <li><code>0.5</code>表示半透明</li></ul> <h3 id="十六进制的rgb值"><a href="#十六进制的rgb值" class="header-anchor">#</a> 十六进制的RGB值</h3> <p>即RGB值的十六进制写法</p> <ul><li>语法：<code>#RRGGBB</code></li> <li>范围：每种颜色的范围在00~ff之间</li> <li>如果颜色两位重复可以进行简写，如 <code>#AABBCC</code> =&gt; <code>#ABC</code> <ul><li>在vscode中，我们可以看到其对于颜色进行预览展示，并且将鼠标移至color处悬停，会弹出rgb调色板，方便我们进行调色。</li></ul></li></ul> <h3 id="hsl"><a href="#hsl" class="header-anchor">#</a> HSL</h3> <ul><li>语法： <code>HSL(色相， 饱和度， 亮度)</code></li> <li><code>H</code> 色相 0~360</li> <li><code>S</code> 饱和度 0%~100%</li> <li><code>L</code>亮度 0%~100%
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